Commit 6e3cf5df authored by Martin Galvan's avatar Martin Galvan Committed by Peter Maydell
Browse files

target-arm: Fix resetting issues on ARMv7-M CPUs 



When calling qemu_system_reset after startup on a Cortex-M
CPU, the initial values of PC, MSP and the Thumb bit weren't being set
correctly if the vector table was in ROM. In particular, since Thumb was 0, a
Usage Fault would arise immediately after trying to execute any instruction
on a Cortex-M.

Signed-off-by: default avatarMartin Galvan <martin.galvan@tallertechnologies.com>
Message-id: CAOKbPbaLt-LJsAKkQdOE0cs9Xx4OWrUfpDhATXPSdtuNw2xu_A@mail.gmail.com
[PMM: removed an incorrect comment]
Reviewed-by: default avatarPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: default avatarPeter Maydell <peter.maydell@linaro.org>
parent bfb27e60

target-arm/cpu.c

+22 −10
Original line number Diff line number Diff line
@@ -129,22 +129,34 @@ static void arm_cpu_reset(CPUState *s) 
    env->uncached_cpsr = ARM_CPU_MODE_SVC;

    env->daif = PSTATE_D | PSTATE_A | PSTATE_I | PSTATE_F;

    /* On ARMv7-M the CPSR_I is the value of the PRIMASK register, and is

       clear at reset.  Initial SP and PC are loaded from ROM.  */

     * clear at reset. Initial SP and PC are loaded from ROM.

     */

    if (IS_M(env)) {

        uint32_t pc;

        uint32_t initial_msp; /* Loaded from 0x0 */

        uint32_t initial_pc; /* Loaded from 0x4 */

        uint8_t *rom;



        env->daif &= ~PSTATE_I;

        rom = rom_ptr(0);

        if (rom) {

            /* We should really use ldl_phys here, in case the guest

               modified flash and reset itself.  However images

               loaded via -kernel have not been copied yet, so load the

               values directly from there.  */

            env->regs[13] = ldl_p(rom) & 0xFFFFFFFC;

            pc = ldl_p(rom + 4);

            env->thumb = pc & 1;

            env->regs[15] = pc & ~1;

            /* Address zero is covered by ROM which hasn't yet been

             * copied into physical memory.

             */

            initial_msp = ldl_p(rom);

            initial_pc = ldl_p(rom + 4);

        } else {

            /* Address zero not covered by a ROM blob, or the ROM blob

             * is in non-modifiable memory and this is a second reset after

             * it got copied into memory. In the latter case, rom_ptr

             * will return a NULL pointer and we should use ldl_phys instead.

             */

            initial_msp = ldl_phys(s->as, 0);

            initial_pc = ldl_phys(s->as, 4);

        }



        env->regs[13] = initial_msp & 0xFFFFFFFC;

        env->regs[15] = initial_pc & ~1;

        env->thumb = initial_pc & 1;

    }



    if (env->cp15.c1_sys & SCTLR_V) {